just last night i started to take apart my '03 wr450. (reason; i was kick starting the bike the other day, and the kick-start kicked me back. i thought i had broken my foot, it hurt so much! the kick-start came back to the top in a real hurry and the engine ceased right where it stopped. it took a lot to actually get the motor to turn again, and just as it did, it made a grind somewhere, and i don't know where yet! after the pain had subsided, i did get the bike started, but it was now making a knocking noise. it was sporadic, not rhythmic.) so, i now have three questions; what is making the knocking sound, where did the engine cease, and why did the kick-start kick me back? first thing i did was check the valves, and they will need shim'n, but not much! i then pulled the head and cylinder and piston off. head and piston where both black (looks like it was running hot. feed-back on this would be great), valves and seats look fine so far, but i may have them machined if need be. The piston pin does have some grove marks from piston or rod!?!, i will replace this. in fact, after i took off the piston clips, the pin would not slide out easily. it did have play side-to-side now with he clips removed, but the pin needed to be punch out. i don't think this was the cause of the cease-up or knocking, but....... the rod has just a little side-to-side movement, but only very little! the rod does not seem to have any up and down play. (solid crank and bearings, i hope!) The cylinder, it looks great. no markings or scratches, it still has cross honing from factory. but at the very top of sleeve you can see burnt or brown coloured tint to it. maybe cause the rings don't go that high. (i will get a closer look soon). the rings look like they have been stretched and will need replacing, but otherwise seem ok. again, sleeve looks clean, except for the very top. to look at the crank, it has some blue heat marks on it, but runs smooth and has no play that i can find so far. note the rod with what seems to be rust. is this normal? i will replace. the engine did get wet in '04. i will be taking the engine off the bike this weekend and probably splitting the case to rebuild. i will follow-up with pics. quick note on the kick back of the kick-starter. it has happened before, never to this extreme, but it has kicked back before. i was getting use to the bounce at the bottom of the kick, and having to hold down, but it has progressively gotten harder to hold down as time went on. the auto decomp on the cam seems fine!?! i have stopped using the e-start awhile back. one more thing i have to look at on the rebuild. replace '03 parts, or remove all-together????